Bail-out parachute systems typically comprise a harness, a container, a pilot parachute (the "pilotchute"), and a main parachute. In most modern parachutes, a rip cord is used to pull out a locking pin, allowing a launching spring to eject a pilotchute into the air stream. Once the pilotchute enters the air stream it inflates and pulls the main parachute out. The line attaching the pilotchute to the main parachute is called a "bridle". This bridle is often routed through a deployment device. On some parachutes the deployment device, usually a small bag, will be attached to the pilotchute, but not to the main parachute. These are known as a free bag deployment systems. The deployment device provides stowage for the main canopy and suspension lines, ensuring a more orderly deployment of the parachute, and thus a more reliable parachute deployment system.
Details on the current state of the art on U.S.-manufactured personnel parachutes, their materials, design, construction, repair, and packing may be found in THE PARACHUTE MANUAL, A Technical Treatise on Aerodynamic Decelerators, by Daniel F. Poynter, Para Publishing, P.O. Box 4232, Santa Barbara, Calif. 93103-0232 (1984), which is expressly incorporated by reference herein. U.S. military specifications for personnel parachutes are presented in Military Specification MIL-P-85710(AS), Parachutes, Personnel, Emergency Escape, General Design Specification for, Department of Defense, Washington, D.C. 20301, Mar. 5, 1986, which is also expressly incorporated by reference herein.
The life of a parachute system is affected by (1) the wear due to the inspection and repack cycle, and (2) the deterioration during service caused by aging of the parachute materials. Materials age because of environmental effects, such as moisture, oxygen, ozone, smog and ultraviolet light, because of wear, and because of the incompatibility of different materials used in constructing the parachute system. For example, the emergency parachute system used most frequently by the Navy is the NB-8 system. The NB-8 system is currently inspected and repacked every 440 days. The typical service life of a nonejection-seat personnel parachute such as the NB-8 is about seven years. On the other hand, vacuum-packed ejection-seat personnel parachutes have demonstrated a service life of up to 20 years. These systems have a proven ability to maintain their package integrity for at least five years even with repeated handling.
The NB-8 system is also heavy and bulky. It weighs over 25 pounds because it uses metal closing cones, metal container opening springs, a spring steel stiffener for the container, and four rip cord pins. When packed, the NB-8 system is about 6 inches thick, and has a volume of about 1,100 cubic inches.